You cannot rely on solvent recovery for your calculations and you cannot avoid a sample cleanup! The use of surrogate compounds (isotopically labeled PAHs) and injection standards is mandatory. There are literally thousands of accessible protocols for this kind of analysis for you to explore, the choice depending also on the goals of your work.

What I am saying here is that I spike blank filters with known conc. of my target PAHs and than extract with sonication clean up with PFTE filters evaporate and reconstruct to 1 ml and add internal standards(deuterated). What i am worried about is that i add 10 ml of DCM for instance and i cannot squeeze more than 6 ml from the filter after extraction of that initial 10 ml so I have this 4 ml loss. So i am worried how i overcome this.

Spiking with surrogate standards is when I spike loaded filter to examine matrix influence.

 I am developing a method for monitoring PAHs in the Air (trace analysis) GC/MS SIM mode Internal standard calibration.

You may refer to BIS method IS 5182 (Part 12):2004 and USEPA method (TO-13)

You will get evaporative loss with sonication, and never get 100% of solvent back.  Quantitative analysis would require 3X extraction of solid matrix.  So sonicate with 10 mL, drain - repeat two more times.  So you would be sonicating each filter 3X with a total of 30 mL (3x10mL).  This way any residual PAH's left on the filter would be captured in subsequent extractions.  Loss of solvent is not an issue and does not need to be "accounted for".  Your final volume (1mL) is all that matters.

If you are doing PAHs in air however you would need to use a PUF or XAD resin trap post filter as the filter will only capture PAH associated with particulate, and these will volatilize rapidly.   Click on small attachment for wording from TO-13A describing this.

Link to TO-13A Method

http://www.epa.gov/ttn/amtic/files/ambient/airtox/to-13arr.pdf

 Thank you for your help I appreciate it!

I use sometimes TO-13A method sometimes as guide, but its quite old and recommends soxhlet extraction.

Anyhow, I did this procedure 3x and recoveries are quite good except for lighter PAHs(first4 from 16EPA list). 

What I wonder is should I be concerned at all about recoveries of the gas phase PAHs with QFF filters(blank filter spiking for recoveries determination).Or to do the same sample prep procedure as for QFF filters with PUF filters that I m gonna use for gas phase PAHs trapping to determine recoveries of Gas Phase PAHs?

Thank you!

Only way to tell is to try it. You may be losing your more volatile PAHs by sonication technique.  Try just doing a shake (or vortex) of the filters in a 40 mL VOA vial to see if the loss is from sonication, same way (3X). You also might want to do an experiment with 50/50 methylene chloride:acetone to see if that solvent combination gets better recoveries, this is what most people use for extraction solvent.  When we do PUFs we used to set them up in soxhlet, now we use PFE (Pressurized Fluid Extractor).

We use shaking (high speed vortex multi mixer) with 10 mL of DCM and 1 mL of methanol (wetting agent). 3 one minute extractions with 10 mL, combine extracts, concentrate. Direct GC-MS analysis, no cleanup required. As Peter points out, filters are only a part of the trapping system. You need to make sure you back the filter with (my preference) XAD.

3 times 1 minute extraction? That is amazing are the recoveries within 80-120%

What is your experience, does cutting a filter in small pieces enhances extraction efficiency? I have started with 3x15 min with DCM only, recoveries are good except last 3 PAHs form 16EPA list (60-70%). So far I have used 50 ml centrifuge (FALCON) tubes (plastic), does it has to be in glass amber vials?

You should use recovery standards like deuterated PAHs. You add known concentration of recovery standards on the filter before extraction. And after extraction, cleanup, evaporation and analysis you can count losses according to recovery of these standards. You should also sonicate your filters 3times (each in 20ml of solvent) for 30 minutes.

Cutting the filters does help from our experience; better solvent contact.

Spike recoveries are normally within 70-130%. You do get poorer recoveries for the heavier PAHs relative to the lighter ones, but they' still well within our 70-130% limit. If you substitute acetone for the methanol you'll get a slight enhancement of the heavier PAH extraction efficiency.

I agree with Kamil. We spike with the standard USEPA 8270 deuterated surrogates (spiking with the deuterated analog of each PAH is a different method). We have run sonication versus high speed shaking studies and have found sonication to give us poorer recoveries for the lighter PAHs.

i have optimized sample prep method, all recoveries are above 80%. What I am not sure now is:

Recoveries I calculate by spiking BLANK filter with all 16 EPA PAHs (mixture) standards. And add before injection internal std mix to correct injection volume errors due to manual injection I am performing. 

Do i need to get surrogate standards as well (Is it must!)?? To spike LOADED filters as well prior extraction , or this is enough? 

Or maybe I could use classic external calibration method, and spike loaded filters with this internal standard mix I already have (they are all deuterated)

Thank you very much for your help, I appreciate!